For instance, when a worker carries out a work in an environment with virus, bacteria, or the like being afloat therein, it is necessary to prevent the worker from being infected with the virus, the bacteria, or the like. As some examples of the case when a worker carries out a work in an environment with virus, bacteria, or the like being afloat therein, such cases are conceivable where a medical personnel, a rescue worker, an epidemic researcher, etc. contacts a patient infected with respiratory virus, such as influenza virus, or where a worker is to sterilize a poultry house where avian influenza has occurred.
Conventionally, for the prevention of viral/bacterial infection, there is known a construction comprising an air intake portion for introducing ambient air, a cover member for covering a worker's nose and mouth, and a flexible tube for establishing communication and connection between the air intake portion and the inner space of the cover member, wherein inside the air intake portion, there is provided a filter allowing passage therethrough of the intake air from the air intake portion, and this filter is configured to prevent passage of the virus/bacteria (such technique like this is a widely used well-known technique, not allowing citation of any specific prior-art document).